What is a market?

He defines a market by first defining what a market transaction consists of:

...an exchange that is voluntary: each party can veto it, and (subject to the rules of the marketplace) each freely agrees to the terms.
A market is a forum for carrying out such exchanges. ~ p.6

Perhaps you were expecting more from a definition of what a market is and there is definitely more that MacMillan has to say about how they evolve and what causes them to function effectively or not. I hope to return to discussing ideas from this book in the future, but for now I want to pair this book with another book like you might pair a particular wine and cheese for synergistic effect.

What is traffic?

To define what traffic is, Tom feels it is first necessary to be clear
about what a road is:

The road, more than simply a system of regulations and designs, is a place where many millions of us, with only loose parameters for how
to behave, are thrown together daily in a kind of massive petri dish in which all kinds of uncharted, little-understood dynamics are at
work. There is no other place where so many people from different walks of like - different ages, races, classes, religions, genders,
political preferences, lifestyle choices, levels of psychological stability - mingle so freely ... for most of its long life the word traffic has had positive connotations. It originally referred (and still does) to trade and the movement of goods... the movement of goods and people were intertwined in a single enterprise; after all, if one was going somewhere, it was most likely in pursuit of commerce. This is still true today as most traffic problems occur during the times we are all going to work, but we seem less likely to think of traffic in terms of motion and mobility, as a great river of opportunity, than as something that makes our lives miserable. ~ pp. 6 - 7.

How are markets and traffic related?

The study of physical traffic can be rich source of metaphors for how markets evolve and function. Traffic is interesting to study in its own right
because we are all subjected to it and perhaps for that reason it can offer a rich source for metaphorical comparisons to how markets work. Indeed, the definition of what a road is above seems to capture the idea of what a market is better than MacMillan's definition.

MacMillan's preferred way to think about markets is using the metaphor of primitive football and how it evolved from primitive football into the official sports of soccer, rugby, and football. Many of the same dynamics of how markets evolve over time are on exhibit in the evolution of primitive football into these three official sports. The rules and regulations loosely define these different sports much as the rules and regulation loosely define what a road is. By looking at the historical evolution of sports and roads, we can see how rules and regulations were crafted to evolve these sports and road into high traffic systems.

In addition to using traffic as a metaphor for thinking about markets, we might also view a market more literally as the situation where there is traffic to a product or service. While traffic may not be sufficient to define what a market is, it is probably a necessary condition for defining what is or is not a viable market.

These are just some preliminary thoughts to what markets are, what traffic is, and how they are related. I hope to revisit some of these themes in the future as I (slowly) make my way though these books. My aim is to have a richer understanding of these two fundamental concepts and their interrelations.